The military diet is a variation of the ever-popular three-day diet, a crash plan of “fill-in-the-blank” foods to eat if you want to lose weight fast. These diets typically claim that you can lose about 10 pounds in three days to a week if you follow their blueprint to the letter. The meal plans are usually extremely basic and calorie-restrictive, because let’s face it, that’s how you lose weight.

But are these diets healthy? Will the weight stay off?

“With this type of low-calorie, lower-carbohydrate diet, you are losing mostly water and potentially some muscle,” said registered dietitian Elaine Magee, author of “Tell Me What to Eat If I Have Diabetes.” “Water weight drops quickly as the body’s glycogen stores decline, which happens when you restrict carbs and calories. Weight will come back when you begin to eat normally again.”

Could it be that the military diet is different? Here’s a breakdown of what’s prescribed on days one to three of the military diet, with calories calculated via the US Department of Agriculture’s calorie-calculating tool, Supertracker.

Breakfast is a cup of caffeinated coffee or tea, one slice of toast with 2 tablespoons of peanut butter and half a grapefruit. That’s 308 calories.

Lunch is another cup of coffee or tea, a bare-bones slice of toast (whole-wheat is best, they rightly say) and a half-cup of tuna. This meal is tiny, only 139 calories.

Dinner is 3 ounces of any meat (that’s about the size of a playing card), a cup of green beans, half of a banana and a small apple (not a large apple, even though the calorie difference is minuscule), but wait: You get a whole cup of vanilla ice cream! If you choose steak instead of a lean chicken breast as your entree, this meal equals 619 calories.

But even with the steak and the cup of full-fat ice cream, the day adds up to a mere 1,066 calories. No snacks allowed.

“If you’re used to eating 2,000 to 2,500 calories a day, such a drastic drop will be hard to do,” said registered dietitian Lisa Drayer, who writes about nutrition for CNN. “You’re going to be tired and irritable, with difficulty concentrating. It will be hard to exercise, and I would think you’ll be quite hungry as well.”

Here’s day two’s repast. It adds up to only 1,193 calories, even if you pick some higher-fat options.

Breakfast is another dry piece of toast, one egg cooked however you like and half of a banana. Let’s say you fry your egg in oil. That’s 223 calories.

Lunch is a hard-boiled egg, five saltine crackers and a cup of cottage cheese. If you choose full-fat cottage cheese, the total is 340 calories.

Dinner is half of a banana, a half-cup of carrots, a full cup of broccoli, two hot dogs (that’s right!) and another treat: a half-cup of vanilla ice cream. The meal totals 630 calories (if you eat a full-fat pork or beef dog).

How does this fare fair?

“I never recommend hot dogs or any processed meats,” Drayer said, “because they are associated with a higher risk for cancer.”

“Ice cream is not a good use of the meager calories,” she added. “You could have 3 cups of salad and only eat 100 calories, or other nutritious foods that will be satisfying and hold back the hunger.”

Day three is the most restrictive, only 762 calories.

Breakfast is a slice of cheddar cheese with five saltines and a small apple. That’s 232 calories.

Lunch is grim: one dry slice of toast and an egg. Even if you fry the egg in oil again, that’s a total of 170 calories.

Dinner is 460 calories and a stomach-turning combination of half a banana, a full cup of tuna and another cup of ice cream. Maybe they think that by now, you’re so hungry, you’ll be willing to eat those foods together.

The websites promoting the military diet say that eating certain food combinations will boost your metabolism.

“There is no truth behind claims that the food combinations in the first few days will increase your metabolism and burn fat,” Magee said.

“There’s no research I know of behind those claims,” Drayer agreed.

And what about the rest of the week?

You round out your week by eating what you like, so long as it’s less than 1,500 calories a day. Then you can start on the three-day restrictions again.

Best of all, no exercise — zero, zip, nada — is said to be needed on this diet.

“Yet another fad diet that won’t lead to healthy or sustainable weight loss!” Magee said with passion, adding that exercise is “key to lasting weight loss.”

She also feels there are potential physical and emotional ramifications to diets that restrict and deprive you to this extent.

“It can lead to weight cycling, a quick loss and regain of weight, that can weaken your immune system, mess with your metabolic rate and increase the risk of other health problems, such as gallstones and heart trouble,” Magee said.

Why is it called the military diet?

Why would such a fad diet be associated with the military? According to various articles, bloggers, YouTubers and message board posts, it was designed by nutritionists in the US military to drop pounds off recruits who otherwise wouldn’t measure up.

“What? In my 30 years working with the military, I’ve never heard of it,” said certified nutrition specialist Patricia Deuster, professor at the Uniformed Services University and author of the first US Navy SEAL Nutrition guide.

“We did not develop this. We do not use it. It has absolutely no resemblance to the real military diet. Even our rations are healthier and more nutritionally sound,” Deuster said. “It looks like they just took the name ‘military’ and added it to the diet and capitalized on it.”

An Internet search shows that this very diet — down to the hot dogs and ice cream — is also known as the American Heart Association diet, the Cleveland Clinic diet, the Mayo Clinic diet, the Kaiser diet and the Birmingham Hospital diet. What do they have to say?

“The Birmingham Hospital Diet did not originate with the University of Alabama at Birmingham, and we do not support or recommend it,” university public relations manager Bob Shepard said. “This diet has absolutely no connection to UAB Hospital other than the often repeated but false Internet rumors.”

Oh?

“It is unfortunate our name has been associated with this diet,” the Cleveland Clinic said in a statement. “We have never endorsed this meal plan, and it does not meet the standards for what we would consider a healthy diet for heart health or overall well-being.”

And?

“The American Heart Association is not — and never has been — associated with this diet.”

“This didn’t come from us, despite the use of the word Kaiser. Kaiser Permanente supports a balanced diet, rich in fruits, vegetables and whole grains.”

“None of these diets, including the three-day diet, was developed at or ever associated with Mayo Clinic,” said Dr. Donald Hensrud, director of the Mayo Clinic Healthy Living Program and medical editor of the real Mayo Clinic Diet. “It is likely the originators tried to capitalize on Mayo Clinic’s brand recognition as a way of promoting these diets.”

Where did this diet come from?

If you search the Internet for the military diet, you’ll probably end up on the top result: themilitarydiet.com. There, you’ll find the detailed diet, with pictures and tips on how to make it work for you. There are substitutions, frequently asked questions, a blog, a calorie count, a link to like them on Facebook and a review that fights back against nutritionists who debunk the diet.

Oh, and there are lots of ads.

But nowhere on the page is there an author, an expert, a nutritional guru. No one takes ownership of this information or gives you any credentials to prove their expertise.

“That’s a red flag,” Drayer said. “Any helpful diet plan should be created or supported by a credible person or resource or organization. If something is out there without any author or inventor, anyone can say anything and not know how the body works.”

Trying to track down the owners of three of the most popular military diet sites proved to be a dead end. Emails and calls to listed numbers got no responses.

How diet misinformation spreads

“Due to our democratic process, we have a wide-open information environment in the US,” said Brian Southwell, editor of a new book on fake news called “Misinformation and Mass Audiences.” “There’s no careful censoring of false information.”

Add to that the fact that science still doesn’t have the “perfect” solution for weight loss and maintenance, he said, and you’ve got an area that is ripe for exploitation.

“These dieting sites have a catchy name, the promise of lineage to established institutions, and that is what tends to spread across the Internet, instead of a peer-reviewed study,” said Southwell, who directs the Science in the Public Sphere program at the nonprofit research group RTI International. “And just like direct mail, if you get 5% of people to click through, you can make a huge profit. It doesn’t cost much to unleash stuff online.”

Drayer agreed. “I think a lot of people just want to know the next dieting magic bullet, quick fix, and they just go for these fad things.”

But why are so many of us fooled in the first place?

The failure of some people’s “BS detectors” when they encounter fake information can be explained, Southwell said, by what science now knows about how the brain processes data. Instead of sorting the good from bad as the information arrives, the brain accepts it all, “and then in another part of the brain, it’s tagged as true or false.”

“It leaves open this window of opportunity,” he explained, “so people believe just long enough and then get tired, distracted, and what happens? They get sucked in. They might be skeptical at first but fail to do the research and think, ‘well, maybe this will work. This might be my solution.’ ”

The fact that so many of us share our discoveries with friends and loved ones on social accounts fuels the misinformation fire. Southwell calls it “social contagion.”

“It’s like the dynamics of infectious disease. You’ve spread the disease before you’ve even come down with it, ” he explained. “You find it, you share, you read more and find out that it’s not effective, or you try it out and you’re disappointed. But the genie is out of the bottle already.”

According to Southwell, that’s exactly what many of these sites are counting on.

“It doesn’t matter if it ultimately gets debunked, because it’s going to take a while for it to reach the same numbers of people as the original rumor or fake diet,” he explained. “And the debunking is not as sexy as the original diet lure.

“In the meantime, you might see the spread of unhealthy dieting behavior, and for some people with certain diseases or conditions, that can cause real harm,” Southwell said, such as heart disease or diabetes. “But it can’t be traced back. Who is culpable for that?”

Healthy ways to lose fast?

Let’s face it. We still want a quick way to lose 5 or 10 pounds fast, just in time for that special occasion. Is it possible to do so in a healthy way?

“I will prescribe a modified three-day diet just to jump-start weight loss,” Drayer said. “I typically recommend increasing your water intake and eliminating all starchy carbs like breads, pasta, cereal and rice, as well as sweets and treats for one week. Doing this not only cuts calories, but you also shed some extra water too, which can be motivating as the numbers on the scale go down.”

For those who drink their calories, Drayer recommends slashing sugary beverages such as sodas, flavored lattes, fruit juices and smoothies, “as the calories from these beverages can really add up.”

Magee prefers to trick the body into losing weight, to avoid what she calls a starvation backlash.

“When you decrease your calories so severely as they do in the three-day military diet, your body tends to go into conservation mode and actually burns fewer calories,” she said, “because it thinks you are entering a potato famine or similar, and it wants to survive.

“I think it’s better to trick your body into burning calories by decreasing the calories you eat a little, increasing exercise to burn more calories, to create a daily deficit of about 250 calories a day,” she explains. “It’s slower but more sustained weight loss, and you are more likely to lose body fat rather than muscle tissue and water.”

Regardless of what method you try, said Drayer, remember that any diet should be cleared by your nutritionist or doctor before you begin. And when it comes to the three-day military diet, she concluded: “I can’t imagine any doctor or expert endorsing the military diet as healthy or beneficial in any way.”